1. Field of the Invention
The present invention relates generally to the field of matrix printing wherein alphanumeric characters are printed in dot matrix form by the energization of one or a plurality of wire elements, or print hammers, in response to digitally generated character data for driving and controlling or more printing heads, each head including one or more of such print hammers, for sequentially printing lines of characters on a print receiving medium. The matrix printing field also includes non-impact printing such as thermal printing. More particularly, the present invention relates to a matrix printer and a novel print hammer impact energy control therefore for varying the impact energy of the print hammers automatically to compensate for variation in input power supplied to the hammer drive solenoids, thereby insuring substantially constant impact energy of each printing wire as its associated head traverses the printing medium. The present invention also relates to an externally synchronized pulse width modulated circuit for deriving a variable width pulsed output for controlling the hammer impact energy in accordance with changes in input power. The present invention also relates to matrix printing of multiple copy forms.
2. Description of the Prior Art
Modern high speed matrix printers must have print head control capable of printing a variety of character fonts at ever increasing and varying speeds, under varying input power conditions and yet maintain reliability of operation, cost efficiency, durability, uniform character spacing and width and constant print quality. While the actual print head construction does not form a part of the present invention, many configurations are possible, both with respect to the number of print wires and print wire orientations. A typical matrix print head wire matrix drive is illustrated by U.S. Pat. No. 3,690,431.
A timing control of the prior art for a matrix printer is illustrated by U.S. Pat. No. 3,719,781. A dual three-station matrix printer of the prior art is illustrated by U.S. Pat. No. 3,825,681.
A servomotor pulse width control circuit capable of compensating for variations in supply voltage is described by U.S. Pat. No. 3,743,911.